Supervisory control system



Feb 211, 1939. f H. P-QBOSWAU 2,148,044

SUPERVISORY CONTROL SYSTEM Filed May 27, 1952 6 Sheets-Sheet 1 INVENTOR HANS P. BOSWAU H. P. BOSWAU.

SUPERVISOBY CONTROL SYSTEM Feb. 21, 1939.

Filed May 27, 1932' 70 F IG.-/

FIG-2 6 Sfieets-Sheet 2 INVENTOR HANS P. BOSWAU Feb. 21, 1939. I H. P BoswAu 2, 8,

7 SUPERVISORY CONTROL SYSTEM Filed May 27, 19252 6 Sheets-Sheet 3 synchronism Indicator b Metering Reciguc r FIG-3 H. P. BcswAu SUPERVISOR! CONTROL SYSTEM Feb, 21, 1939.

Filed May 27, 1932 e Sheds-Sheet 4 INVENTOR HANS BOSWAU Feb. 21, 1939. HP w-AU 1 2,148,044

SUPERVISORY CONTROL SYSTEM Filed May 27, 1932 6 Sheets-Sheet 5 lA/l/E/VTOI? HANS R BUSH/AU Feb. 21, 1939. H. P. BOSWAU 4 SUPERVISOR! CONTROL SYSTEM Filed May 2'7, 193?. 5 Sheets-Sheet 6 662 TOP/6:5

642-[1' r-vram 652 7-1- Lowl control V v INVENTOR I HANS P- BOSWAU FIG-6 Patented Feb. 21, 1939 UNITED STATES PATENT OFFICE North Electric Mfg. Company, Gallon,

corporation of Ohio Ohio, at

Application May 27, 1932, Serial No. 613,865

Claims.

My invention relates to signalling systems and more particularly to supervisory control systems in which a plurality of remotely disposed apparatus units, such as circuit breakers, are selectively controlled and supervised from a. central dispatching point.

In supervisory control systems it is highly desirable that the selection and operation be performed with the highest possible speed and that the accuracy of the remote selection be ensured beyond a doubt.

I have discovered that I can readily select one out of at least five breakers over a single signalling circuit with a single selecting impulse, which F accordingly requires a minimum amount of time. Similarly, one out of at least twenty-five breakers can be selected With two impulses, thus providing a very high speed of selection. A very important advantage of the high selection speed is that inductive disturbances produced in the signalling circuit by adjacent power lines aremuch less likely to occur during the extremely small period of time required for selection in my system than during the comparatively long period of time required in systems employing long series of impulses for selecting purposes.

Accordingly, an object of my invention is to provide a novel method of signalling.

Another object of my invention is to provide novel apparatus for and methods of. selecting a plurality of units with a single code pulse over a single signalling circuit.

A further object of my invention is to provide novel apparatus for and methods of signalling which will insure correct selection of the remote units.

A still further object of my invention is to provide novel means whereby a remote code selection is also simultaneously set up locally at the sending station and compared with a check code received back from the remote station to determine whether a correct remote selection has been made.

Another object of my invention is to provide metering, synchronizing and voltage regulation in the system described above, all over a single signalling circuit.

Still another object of my invention is to provide, in a supervisory control system, for connecting a meter to a single signalling circuit at one station and a metering transmitter and raise-lower control apparatus to the circuit at another station, and selectively operating the raise-lower control apparatus, the functioning of which is transmitted to the meter by the metering transmitter.

There are other objects of my invention, such as the simplification of circuits, utilizing the same circuits for a plurality of different functions and 5 in inter-related manner which will appear in the following detailed description in connection with the drawings, in which Figures 1 to-3 are the detailed circuit diagrams of the apparatus at the control office and .1

Figures 4 to 6 are the detailed circuit diagrams of the apparatus at a remote substation, the office and substation being connected by two conductors L-l and L-2.

Before describing the circuits in detail a brief description of the principles of my invention will be given, together with a detailed description of the functions of the various apparatus used.

I have discovered novel means for utilizing a code arrangement which comprises five different code combinations suitable for the transmission over a single signalling circuit, namely: a first code consisting of an impulse of continuous direct current of onepolarity, a second code consisting of an impulse of continuous direct current of the opposite polarity, a third code consisting of an impulse of rapidly pulsating current of one polarity, a fourth code consisting of an impulse of rapidly pulsating current of the opposite polarity, and a fifth code consisting of an impulse of alternating current. The pulsating currents may be produced for example by passing alternating current through. a half-wave rectifier or by superimposing alternating current upon direct current of the same or higher peak voltage. The frequency of the alternating current must be such that each selecting impulse contains at least five or more complete cycles of the alternating current.

These codes are utilized to operate receiving 40 relays at the remote station in five diiierent combinations, thus permitting the selection of one out of a total of five selection points with a single impulse. By adding a second impulse, the selection may be increased to 25 points, etc.

For the line receiving relays I have provided relays arranged in special circuits with re'ctifiers, so that one line relay, such as relay IN, is responsive only to a continuous direct current impulse of one polarity or to a pulsating current 50 impulse of the same polarity. Line relay I 02 is responsive only to a continuous direct current impulse of the opposite polarity or to a pulsating current impulse of this opposite polarity and line relay I03 is responsive to an alternating current impulse or to a pulsating current impulse of either polarity, but not to a continuous direct current impulse of either polarity. It will be understood that an alternating current impulse will operate not only relay I03, but also relays IOI and I02, since the alternating current may be considered as being composed of two pulsating currents of opposite polarity.

Two line conductors, or one line conductor with ground return, extend from the office to the substation and are normally associated at each end with the line receiving relays. Proper circuit connections are provided at each end so that the line conductors may be connected to the code transmitting apparatus at one end and to the line receiving relays at the other end, when code impulses are to be transmitted in one direction, and vice versa for transmitting code impulses in the opposite direction.

For selectively controlling and supervising a breaker at the substation the dispatcher first operates an' individual selection key. This sets up conditions at the office for transmitting a plurality of code impulses, for example, one for making a group selection and a second for making a unit selection. The transmitter at the dispatchers office is then connected to the line conductors while the receiving line relays at the substation are normally connected to the line conductors. Thereupon the group selection code impulse is first transmitted over the line conductors, making a group selection at the substation through the operation of the line receiving relays thereat. Following the transmission of the group selection code impulse, a unit selection code impulse is transmitted from the ofiice and, as in the case of the group selection impulse, the line receiving relays at the substation operate in response to the unit selection code impulse for making a unit selection at the substation. Simultaneously with the transmission of the group and unit selection impulses from the oflice to the substation, group and unit selection operations of a corresponding character are performed locally at the office and circuits thereat are prepared for comparing the check-back impulses subsequently received from the substation with the selection made locally at the office.

Following the transmission of the group and unit selection impulses from the ofiice to the substation, the transmitter at the office is disconnected from the line and the line receiving relays thereat are associated with the line. At the substation, the line receiving relays are disconnected from the line and the transmitter thereat connected to the line.

Code transmitter relays at the substation have been prepared by the group and unit selection made thereat for controlling the transmission of a check code back over the line to the oflice. This check code, instead of being transmitted in the order of first group and then unit code as they were received from the ofiice, is reversed, the unit check code being transmitted first and followed by the group check code. At the ofiice, in response to the unit check code, the unit check circuit locally prepared thereat is completed, if it properly compares with the selection locally set up. Similarly, when the group check code is received, the group check circuit is completed, if it properly compares with the group selection locally set up.

If the check codes received back at the oflice indicate the accuracy of the remote selection, the apparatus is conditioned for transmitting a control code from the oflice to the substation to operate the selected unit, when the dispatcher operates the master control key.

During the interim between the checking of the remote selection and the operation of the master control key, the selection made at the substation is maintained by a series of intermittent holding impulses transmitted over the line from the dispatchers oifice. In the intervals between these holding impulses the substation transmits back to the office supervisory impulses indicating at the office the condition of the selected breaker. These intermittent holding and supervisory impulses will continue indefinitely until the dispatcher either releases the selection key or depresses the master control key. When he depresses the master control key the holding impulses are changed to control impulses transmitted over the line to the substation, which operate the line relays thereat to operate in turn the selected breaker.

Upon operation of the breaker to its new condition, the code of the supervisory impulses transmitted back to the office is changed so as to indicate the new condition of the operated breaker by means of supervisory lamps. The apparatus may then be restored to normal by releasing the selection key.

The function of the more important apparatus in my system will now be described in detail, in gs the order in which it is operated.

Relay II I is the start relay which is energized over the contacts of an individual control key, such as 306, in series with one of the code control relays 22I to 225. Relay III is originally energized over a back contact of the holding relay I04 which is subsequently energized, but relay I I I is locked independently of relay I84 over its own front contact. Furthermore, the circuit for relay I I I extends over contacts of group and point code control switching relays H4 and H5 but these contacts are make-before-break contacts, so that the relay III remains energized as the circuit therefor is switched from one to another of the code control relays. Relay II I at one of its contacts controls a circuit for the sending relay I05 and at another contact controls the circuit for the meter releasing relay I59. Relay III also controls the circuit for the auxiliary start relay I I2 which prevents the release of the oflice except after a code has been completed.

Relays 22I to 225 are the sending code relays. These relays are energized selectively in accordance with the selection key operated for controlling the application of the proper selection and checking codes to conductors LI and L-2. Relays 22I, 223 and 224 also control codes for holding the substation selection or for closing and tripping the selected breaker.

Relay 240 is a pole-changer for producing pulsating current in the primary of a transformer for generating alternating currents in the secondary thereof.

Relay I05 is the sending relay. At its contacts it completes the circuit from the transmitting system to the line conductors LP-I and L-2 for the transmission of code impulses. At the same time it disconnects the line receiving relays from the line conductors L-I and L2. Relay I05 is provided with a number of multiple energizing circuits. It may be energized over contacts of the start relay I I I which is energized to start. se lective operations from the office, or over contacts of relay II3 which functions to start checking codes from the ofiice and, finally, it may be eneriii gized from relay II9 which is energized when the checking operations are completed. Relay I05 is deenergized invariably by a contact of relay I06 which functions in cooperation with relay I05 to terminate the transmission of any code impulse originated by relay I05. Relay I85 is prevented from energizing by contacts of line relays NH and I02 so that no code may be transmitted from the oflice while a code is being received from the substation, thus obviating interference between signals.

Relay 229 is the group selection relay for group #1. Relay 230 is the group selection relay of group #2. Additional group selection relays (not shown) are, of course, also used.

Relay IEIB is the sending interrupter relay which is energized by relay Hi5 and which opens the circuit of relay N to terminate the transmission of a code impulse. Both relays I95 and I06 are slow relays so that after relay IIiEi. has opened the circuit of relay I05 a suiiiciently long interval of time elapses to permit the selections to be completed before relay I85 is deenergized.

The slow-releasing feature of relay I05 provides the necessary interval between successive code impulses.

Relay I04 is an extra slow relay which functions as a holding relay for maintaining the selection circuits as long as the system is in operation. This relay is energized over contacts of the line relays or of a relay controlled by the transmitter circuit so that it is energized immediately after the system is started into operation and thereafter remains energized as long as impulses are sent and received. This method of maintaining the selections eliminates the necessity for a special release impulse of a different character for restoring the selections to normal.

Relay II 4 is the group switching relay. This relay energizes in series with a group selection relay, such as 229, 230, etc., at the end of the group selection impulse and functions to switch the selection circuits. from the group selection relays to the unit selecting relays, such as M2, M3, etc., by closing a circuit for the point control relay 223 while opening the circuit of the group control relay 227. Relay H4 is also provided with a make-before-break contact for switching the sending control circuit through the selection key from the group sending code relay to the point sending code relay.

Relay 221 is the group control relay and will be energized for conditioning the group selection relays 5629, 2%, etc., for operation either locally in accordance with a group selection code transmitted to the substation, or from the substation in response to a group selection code transmitted therefrom. Relay 228 is the point control relay and will be energized to condition the point selection relays EIZ, 3I3, etc., for operation, either locally in accordance with a point selection code transmitted to the substation, or in response to a point selection code received from the substation.

Relay H5 is the point switching relay which is energized in series with one of the point selecting relays, such as 3I2, 3I3, etc., at the end of point selection impulse interval. Relay I I5 closes the circuit for the relay H3 which prepares the circuit for checking codes and is also provided with make-before-break contacts for switching the start relay circuit from the point sending code relay to a holding circuit.

Relay II? prepares the office for sending and receiving of check codes. At one of its contacts end of winding it completes one of the circuits for the relay I05, in preparationof sending a check code. It also prepares circuits for the relays H5 and H8 so that if the received check code is identified with the selection locally set up these relays will be energized.

Relay 22B is the check code sending control relay. This relay is energized following the energization of the point switching relay IIE, but only when the substation is the originating end, and controls circuits to the sending code relays 22! to 225 for the purpose of energizing one of these relays in accordance with the group or unit selection relay, energized in response to selection codes received from the substation. Relays 22I and 225 then transmit check signals back to the substation indicating the selection set up at the ofiice.

Relay IOI is a line relay which is connected across the conductors LI and L-2 and in a circuit with the rectifiers I63 so that current can flow only from conductor LI to conductor L--2 in this circuit to operate the relay. Relay I02 is also a line relay and connected in a circuit with rectifiers I62 arranged to permit current to flow in this circuit for operating the relay H32 only from conductor Lr2 to conductor LI. Relays II and I02 also respond to pulsating currents of the same polarity as the continuous direct current to which they respond. The constants of these relays are such that they are suificiently slow in releasing to keep their armatures operated in the intervals between the successive pulsations of a pulsating current impulse. As explained above, an alternating current impulse operates both relays IIlI and I02.

The center points of the rectifiers I62 and I63 are connected together for the following reasons. Whena direct current impulse is sent, for example, through relay IUI, the self-inductance of relay iiJI will tend to maintain the flow of current for a short interval after the impulse has ceased. When the connection of the center points of rectifiers I62 and I63 is omitted, this inductive current surge flows from the upper end of winding It! through resistance I62, relay I62, resistance I64, rectifiers I 63 back to the lower end of winding IIlI and may be sufficiently strong to energize relay I02 momentarily. This difiiculty is avoided by the connection of the center points of rectifiers I62 and I63, which provides a discharge path for the induction current surge from the upper end of winding IIiI through resistance IEI, left rectifier I 62, center connection, left rectifier I63 back to the lower IEII. new discharge path does not include the winding IBJZ, so that relay I I12 cannot be affected by the inductive current surge. Similar considerations hold true when relay N32 is energized by an impulse of proper polarity.

A condenser IE5 is provided between the circuits for relays IIlI and H32 and the circuit for the third line relay I03 to prevent direct current impulses from flowing into circuit of the line relay I03. however, flow through the condenser Hi5 and IBI, rectifiers It will be seen that this Alternating or pulsating currents may;

rectifiers I66 and It? and through relay IE3 to sisting of direct current passing from L-I to L2, will energize relay IOI only, the second code, consisting of direct current passing from L2 to LI, will energize relay I02 only, the third code, consisting of pulsating current passing from L--I to L2, will energize relays IM and I03, the fourth code consisting of pulsating current passing from line L2 to L-I, will energize relays I02 and I03, and the fifth code, consisting of alternating current, will energize relays IOI, I02 and I03. The line relays IOI, I02 and I03 are normally connected across the lines LI and L-2 over the back contacts and armatures of relays I05, I59 and I50. When the dispatchers office is to function as a transmitter, the relay I05 disconnects the line relays IOI, I02 and I03 from the line and connects the office transmitter to the line. Relays I59 and I50 are only energized when remote metering, synchronizing or volt-age regulating operations are to be performed, in which case these relays disconnect the line relays IOI, I02 and I03 and in place thereof associate volt-meters, ammeters or synchronoscopes with the line as the case may be.

Relay H5 is the point checking relay which is energized when a check code has been received from the substation indicating the point selection made at the substation. If this check code agrees with the local point selection set up at the office, relay H6 energizes and in turn prepares a circuit for the point check switching relay I I1.

Point check switching relay H1 is energized following the point check, and switches the check circuits to the group checking relay H8.

Relay I I is the group checking relay which is energized in response to a check cod-e received from the substation indicating the group selection made at the substation. If this check code agrees with the local group selection set up at the office, relay H3 energizes and prepares a circuit for the group check switching relays H9 and I20. It also closes a circuit for the check signalling lamp at the office to indicate to the dispatcher that a correct selection has been made at the substation.

Group check switching relays H9 and I20 are energized following the point check. Relay I20 opens the circuit of the relay I I3 which prepared the system for receiving the check codes. Relay H0 opens the locking circuit for the point checking relay H6 and of the point check switching relay III. These relays may all be deenergized after the check code has been properly identified. Relay I20 prepares circuits for relays 22I, 223 or 224 for controlling the transmission of holding, closing or tripping code signals following the receipt of the check signals.

Relay 208 is the trip supervisory relay which is energized over contacts of line relays I02 and I03, in response to a trip supervisory code received from the substation to control the supervisory lamp relays such as 322, 324, etc.

Relay 209 is the close supervisory relay operated in the same manner as relay 208, except that this relay is operated in response to a closed supervisory code received from the substation.

Relay 2I0 is an anti-pumping relay, which is energized over contacts of relay 208 in response to the receipt of a close supervisory signal, and prevents the transmission of further operation control codes which would keep the breaker closed in the event that the breaker has been automatically tripped as the result of a short circuit.

Relay 207 is the master control relay controlled by the master control key. The energizing circuit for the relay 201 is completed over a front contact of relay I03 and a contact of the master control key. When the master control key is depressed, relay 20! accordingly will not be immediately energized if a holding pulse is being transmitted at that time, but must await the receipt of an impulse from the substation. This prevents mutilation of the holding code. When a supervisory impulse is received, which in the present embodiment of my invention invariably comprises a pulsating impulse, the line relay 03 at the office is energized to complete the circuit for relay 207. Relay 201 in turn controls the transmission of the breaker operating code.

Relay 23 i is an alarm relay, energized in response to a trip supervisory signal to indicate an automatic trip operation received from the substation.

Relay 235 is a disagreement lamp flashing relay which is operated when the individual control key is in disagreement With the condition of the remote unit.

Relay 235 is also a disagreement lamp flashing relay cooperating with relay 235.

Relay I 58 is energized to: prepare the cffice for metering.

Relay let is energized toswitch the circuits to metering.

Relay 50 releases the metering set-up.

Relay I80 is an auxiliary to relay I50. Relays M2, M3, etc., are the point selection relays. lays 3'22, 324, etc., are the supervisory lamp relays.

At the substation relays 005 to 406, M3 to 520, 45%, 524 to 530 and 500 function in a similar manner to the corresponding relays IOI to H3 to 62s, i 39, I50, 22I to 230 and 200 at the office.

Relay 40! operates after a supervisory code I is transmitted to the oflice for preventing the substation from transmitting further codes until a code has been received from the office.

Relay 4H is the start relay operating when an operation is started from the substation. Relay 492 is a start delay relay to give the dispatcher preference over any automatic operations originating at the substation.

Relay 4S0 prepares to release the metering. Relays 5V2, 6E3, etc. are the point selection relays.

Relay 500 is a trip control relay, responding to the trip control code from the office to trip the circuit breaker. Relay 509 is a close control relay responding to the close control code from the office to close the breaker.

Relay 559 changes the voltage regulation circuit from raising to lowering.

Relays 522, 624, etc. are the point starting relays functioning to start the substation when an automatic operation occurs, and relays 632, 63 etc. are the point supervisory relays controlled by the circuit breaker.

In order to more clearly explain the invention, the operations which occur when the dispatcher desires to selectively control and supervise a breaker will now be described.

Normally a circuit is completed at the oifice from positive battery over armature I-a and its back contact of relay I20, armature II ib and its back contact of relay 1 I4 and through the winding of relay 22'! to negative battery. The energization of relay 221 prepares circuits for the group selection relays 229, 230, etc., which circuits will be completed later by relays IOI, I02, and I03, or 22I, 222, 223, 224 and 225.

At the substation the relay-52! is normally energized over a similar circuit from positive battery over armature 420-a, and its back contact, armature- 4I4-b and its back contact and through the winding of relay 521 to negative battery. At the substation, the point start relays 622, 624, etc., are also energized over bvious locking circu1ts.

In order to start operations for the purpose of remotely controlling and supervising a circuit breaker, the dispatcher operates a point selection key, such, for example, as. the key 305. As a result of the operation of the key 3% a circuit is completed for the relays Ill and 22! in series from positive battery over armature ltd-b and its back contact of relay I04, armature Mfi-b and its back contact, through the winding of relay III, break contact of armature II-a, break contact of armature II4-a, through the closed contacts 3Il6-c of key 306, and through the winding of relay 2'2I to negative battery. Relays I II and 22! are energized over this circuit. Relay III, upon energization, locks itself over a circuit from positive battery over armature III-b and its front contact, through the winding of relay III, and thence over the circuit including break contact of armature II5-a and break contact of armature H t-a, as traced above, through key 306 and windng 22! to negative battery. A further result of the energization of relay III is to completea circuit for relay IIZ from positive battery over armature III-a and its front contact through the winding of relay H2 to negative battery. A locking circuit is prepared for relay II 2 at the front contact of its armature M 2-11, but this circuit is not completed at this time.

A further result of the energization of relay III is to complete a circuit for the pole-changer 240 from positive battery over armature III-a and its front contact through back contact and armature I04-a through armature H2 and its back contact and through the winding of polechanger 240 to negative battery.

The pole-changer 240 is energized over a circuit which is interrupted by its own armature 2| 2, causing this armature to vibrate. The vibrating armature closes a circuit extending from positive battery over armature III-a and its front contact, and back contact and armature I04-a, through armature 2I2 and its contacts alternately through one or the other half winding of the primary of the transformer 206, and through a resistor to negative battery. Accordingly, as the po1e-changer armature vibrates, current is flowing first in one direction and then in the opposite direction through the primary of transformer 20E, inducing an alternating current in the secondary winding. This alternating current is subsequently used for transmission of signalling codes.

A still further result of the energization of relay III is the completion of a circuit for the sending relay I05 from positive battery, through armature I02-a and its back contact of relay I 02. armature I Ill-a and its back contact, armature III-c and its front contact, back contact and armature II5-b armature I06-b and its back contact through the winding of relay I 05 to negative battery. At this time relays I05, I I I, H2, 225, 221 and 240 are energized. As a result of the energization of the sending relay I05, a circuit is now completed for the group selection relay 229 of group #1 from positive battery, through back contact and armature II3-a of relay II3, through armature I05-c and its front contact of the energized relay I05, through armature II9-c and its back contact, armature 22I-c and its front contact of relay 22I, armature 22'I-a and its front contact through the winding of relay 229 to negative battery. Relay 229, upon energization, functions to select the desired group and prepares a circuit for relay II4 over armature 229-a and its front contact, winding of relay II4 to positive battery supplied over armature II2-a and its front contact and front contact and armature III-a, but this circuit is not efiective at this time due to the bypassing circuit around the winding of relay II4 extending over the original energizing circuit for the relay 229 described above.

A further result of the energization of the sending relay I05 at the ofiice is to control the transmission of the first or group selection code at the front contact of armature I05-a.

Upon energization of the sending code control relay 22I, described hereinbefore, a circuit for the transmission of the code was prepared at the front contacts of its armatures 22I-a and 22I-b. This circuit is now completed upon energization of relay I05, the circuit extending from positive battery at the oflice o'ver armature 22 I-a and its front contact over conductor L-I to the substation, through the resistor 464, rectifiers 463, winding of relay 40I at the substation, back contact and armature 450-11, back contact and armature 405-a over the conductor L-2 back to the office through armature I05-a and its front contact, armature 22I-b and its front contact and through a resistor to negative battery.

A further result of the energization of relay I05 is to complete a circuit for the sending interrupter relay I06 from positive battery, through armature I02-a and its back contact of relay I02, armature IOI-a and its back contact, armature I05-b and its front contact and through the winding of relay I06 to negative battery. Relay I00, upon energization, completes a circuit for relay I04 from positive battery, through armature I06-a and its front contacts and through the winding of relay I04 to negative battery, and also opens the circuit of sending relay 505 at the back contact of armature IUIi-b. Relay I04 is a holding relay which is held operated by impulses sent or received and holds the selection relays locked in. At this time, in addition to the relays described above as energized, relays I04, I06 and 229 are energized, and slowto-deenergize relay I05 is about to drop out, because of its circuit now having been opened.

At the substation, as a result of the energization of relay 40 I, a circuit is completed for group selection relay 529 of group #1 from positive battery, through back contact and armature 4I3-a of relay 4I3, armature 405-0 and its back contact, armature 4IJI-b and its front contact, ar-

mature 402-19 and its back contact, armature 403-a and its back contact, armature 521-11 and its front contact and through the winding of the relay 529 to negative battery.

Attention is called to the special circuit arrangement in which the sending code controlling relay I05 at the ofiice not only controls the transmission of a code to the substation, but also makes a corresponding group selection locally at the ofiice by energizing relay 229. This, it will be noted, is made possible by providing multiple energizing circuits for relay 229 at the office and its corresponding relay 529 at the substation.

Tracing the circuit of relay 229 at the office, it will 'be observed that this circuit may be completed over armature 22I-c of relay 22!, which is a sending code control relay operated when a code is being transmitted from the office, or relay 229 may be energized over armature IOI-b and front contact of the line receiving relay IOI, which is operated in response to a code received from the substation.

In the former case, that is when a code is being transmitted, relay I05 is energized and the circuit for relay 229 is completed over the front contact I05c of that relay. In the latter case, that is, when a code is being received from the substation, the relay I05 is deenergized and the circuit for relay 229 is completed over the back contact I05c of relay I05. Similar circuit connections prevail for the other group selecting relays 230,-etc. Also, at the substation, the corresponding group selecting relays may be energized in response to a code transmitted therefrom or by a code received from the oflice.

The result of such a circuit arrangement is that upon transmission of a selection code from either the office or the substation, simultaneous selections are made at the transmitting station and at the receiving station which, as will appear in more detail hereinafter, prepare circuits for the check operations to identify the remote selection made at the receiving station.

A result of the energization of relay 40I at the substation is to complete a circuit for the relay 404 from positive battery over armature 402-a and its back contact of relay 402, armature 40 I-a and its front contact and through the winding of relay 404 to negative battery. Relay 404 is the holding relay and, as will appear in the following, is operated by impulses sent or received and holds the selection relays locked in. In multiple with the relay 404, the relay M2 is energized from positive battery over armature 402-0, and its back contact, through armature 40l-a and its front contact, through break contact of armature 4i2a and through the winding of relay M2 to negative battery. Relay 4I2 upon energizing, closes a lockingcircuit for itself over the armature 4I2-a and its front contact and front contact and armature 404-b to positive battery. Relay 2 is a start delay relay which functions to delay the restarting of the substation after an operation has been completed, for the purpose of giving the dispatcher preference in seizing the line.

Relays 404 and M2 open the circuit of the start relay 4| I, so that no operation can be originated from the substation until the operation originated at the office is completed. Energization of relay 404 completes a circuit for the pole changer 540 from positive battery over armature 404--a and its front contact, armature 5I2 and its back contact of pole-changer 540 through the winding of pole-changer 540 to negative battery. The pole-changer 540 functions to produce alternating current in the secondary winding of transformer 506, as described above for the corresponding apparatus at the office.

At the office the slow relay I05 has at this time become deenergized and, accordingly, the locking circuit for the relay H4 in series with relay 229 now becomes effective because of the fact that the original energizing circuit for relay 229 has now been opened at the front contact of the armature I05c of relay I05.

Deenergization of relay I05 opens the impulse circuit over the conductors LI and L2 traced hereinbefore and deenergizes the relay 40I at the substation. The relay H4 at the oflice is the group switching relay which, upon energization, prepares the transmission of a second or point selection code. At its break contact of armature II4a, it opens the circuit for relay 22I which had been energized upon the operation of the key 306. A further result of the energization of relay H4 is the completion of a circuit for relay 222 from positive battery over armature III-b and its front contact of relay III, through the winding of relay III, break contact of armature Ii5a, armature II4a, and its front contact, armature 229g and its front contact, through the contact 300b of key 306 and through the winding of relay 222 to negative battery. It will be noted that this circuit is completed over the front contact of armature III-b of relay III which, upon its previous energization, was locked over its own armature energization of the relay II4 whose armature II4--a is a make-before-break armature, maintains itself locked over the circuit described above. Relay 222, like relay 22I, is a sending code control relay which will control the transmission of the point selection code in the manner to be described hereinafter. A still further result of the energization of relay [I4 is to open at armature II4b the circuit for the group control relay 221 which, as will be recalled, prepared a circuit for a particular one of the group selection relays 229, 230, etc.

A still further result of the energization of relay H4 is to complete a circuit for relay 228 from positive battery over armature I20-a and its back contact of relay I20, armature II4--b and its front contact, armature 1-0 and its back contact, and through the winding of relay 228 to negative battery. Relay 228 is the point .control relay which, as will be shown in the following, controls the energization of the local point selection relays 3I2, 3I4, 32I, 322, etc. At this time relays I04, I06, III, H2, H4, 222, 228, 229 and 240 are energized at the ofllce and a point selection code is about to be transmitted.

The operations thus far performed may now be summarized as follows. Upon the operation of key 306 a circuit was completed for the sending code relay 22I which at its armatures 22 I--a and 22Ib prepared circuits of a predetermined polarity from the positive and negative sides of the battery at the office to the conductors LI and L2. These circuits were subsequently completed upon the energization of relay I05 for the transmission of the group selection code. The energization of the start relay III in series with the sending code control relay 22I had completed a circuit for the auxiliary start relay H2. The sending code relay 22I, in addition to controlling the code impulse transmitted over the conductors LI and L2, also prepared at its armature '22 I-c a circuit for the local group selection relay 229 of group #1 to prepare a group selection at the office.

The energization of the relay I05, which, as will be recalled, controlled the transmission of the group selection code, energizes the relay I08 which in turn opens the circuit for relay I05 to terminate the transmission of this group selection code. Relay I06 also completes a circuit for the holding relay I04, which functions to hold the selection relays locked. Group selection relay 229 locks in series with relay II4 after the group selection code has been terminated by the deenergization of the relay I05 and relay -II4,

III-b and, upon the r upon energizing, in turn deenergizes the sending code relay HI and energizes in its place the sending code relay 222 in preparation of the transmission of the units or point selection code.

At the substation the receipt of the group selection code impulse had energized the relay it! which in turn energized the group selection relay 529 for group #1 and also the holding relay te l which provided a locking circuit for the relay 529 in series with the relay 4H5 when the relay ml! was subsequently dropped out at the termination of the group selection code. A circuit was also completed for the start delay relay M2.

Following the energization of the relay M4 at the substation the group control relay 52?, which is normally energized when the set is in non-operating condition, is deenergized and a circuit is completed for the point control relay 528 from positive battery over armature A2B--a and its back contact of relay no, armature 4 M-b and its front contact, armature M'l-c and its back contact and through the winding of relay 528 to negative battery. At the substation there are energized at this time relays 4M, M2, M4, 528, 529 and 54!].

Returning again to the oillce, where a point selection code has been prepared for transmission to the substation upon the deenergization of the slow sending relay I05 following the transmission of the group selection code, the circuit for the slow relay I06 .was opened at the armature lil5b of relay I05. Slow relay Hi6 drops out after an interval and again completes the circuit for the relay I 95. Relay Hi5 again energizes over the circuit traced hereinbefore and at its armature again completes the transmission of a code, this time a point selection code, over conductors L-i and L-2. Inasmuch as the relay 22! is now dropped out and in place thereof the relay 222 is energized, positive battery, instead of being applied to conductor Li over the armature 22|-a and its front contact of relay 22!, is applied to the conductor L-2 over the armature 222-4) and its front contact of relay 222. Negative battery, instead of being .applied over the armature 22l-b and its front contactto the conductor L-Z, is applied over the armature 222-4) and its front contact of relay 222 to the conductor L-l. Accordingly, an impulse of the reverse polarity is transmitted for making the point selection. At the office, in response to the energization of relays 228, 222 and Hit, a circuit is completed for the point selection relay M2 from positive battery through back contact and armature Hit-11, armature iil5c and its front contact, armature I lQ-c and its back contact, armature 22 l-c and its back contact, armature 222c and its front contact, armature 2 2llb and its front contact, through armature 229-c and its front contact, through the winding of the point selection relay M2 to negative battery. Relay 3l2 energizes and prepares a locking circuit for itself in series with relay H5, which becomes effective at a later stage.

A further result of the energization of relay N35 is to complete a circuit again for the slow relay IE5 which at its armature let-11 opens the circuit for the slow relay Hi5 and the relay Hi5 will drop out after an interval of time during which the operations about to be described will be completed.

At this time relays I04, I05, I05, Ill, H2, H4, 222, 228, 228, 240 and 312 are energized at the office.

Referring now to the operations at the substation in response to the receipt of the point selection code, it will be recalled that, as distinguished from the group selection code, positive battery was applied to the conductor 19-2 and negative battery was applied to conductor L-I. The arrangement of the rectifiers 462 and 453 is such that current in this direction can pass only through the line relay M32 at the substation. At this time relays 402, 404, M2, M4, 528, 529 and E i? are energized at the substation and a circuit is completed for the point selection relay 6 [2 from positive battery through back contact and armature ll3a, armature 4il5c and its back contact, armature Mill) and its back contact of relay M l, armature 4fi2-c and .its front contact of relay M2, armature 4il3-b and its back contact, armature 528-2) and its front contact, armature 529-4: and its front contact through the winding of relay il2 to negative battery. Relay EH2 energizes and prepares a locking circuit for itself in series with relay H5 which, however, is not effective at this time due to the Icy-passing circuit around the winding of relay M5 over the original energizing circuit for relay M2 traced above. After an interval of time, however, the point selection code impulse transmitted from the ofiice is terminated upon the deenergization of relay IE5 and the circuit for relay 402 is accordingly opened. Relay 492, upon deenergization, opens the original energizing circuit for the relay M2 and the locking circuit is thereupon completed for the relays BIZ and M5 in series from positive battery over armature Mi l-12 and its front contact of relay 404 through the winding of relay M5, front contact and armature 6l2-a through the winding of relay 512 to negative battery. Relay M5 is the point switching relay which completes a circuit for check sending control relay 525 from positive battery over armature Mil-a. and its back contact of relay 42!], armature 4|5c and its front contact, armature 4i |--c and its back contact through the winding of relay 526 to negative battery. Relay 525, as will appear hereinafter, now functions to control the transmission. of a check code back to the office.

At the office, it will be recalled that the last operation described was the energization of relay H35 which opened the circuit of the slow relay I05. After the slow relay I85 drops out, the

locking circuit is completed for the relay M2 in series with the relay H5 from positive battery over armature Hi l-b and front contact of relay HM, through the winding of relay H5, front contact and armature SiZ-a through the winding of relay M2 to negative battery. Relay M5 is the point switching relay which, upon energization, prevents the transmission of further selection codes.

As a result of the energization of point switching relay M5 the circuit for the relay 222 is opened at the armature lib-11 of relay H5 and relay 222 is thereupon deenergized. Relay l i, however, remains energized over a circuit from positive battery, armature ill-b and its front contact, winding of relay Hi, armature lilia and its front contact, and contact SUB-a of key 3%, to negative battery through resistor 39?. A further result of the energization of relay H5 is to complete a circuit for relay H3 which prepares the system for the checking code to be received from the substation. The circuit for the relay H3 may be traced from positive battery over armature i2iI-a and its back contact, armature Il5--c and its front contact, armature I l2-c and its front contact, through the winding of relay E53 to negative battery. By this time the slow relay NEE, the circuit of which was opened upon deenergization of the relay B85, is also deenergized.

It will be recalled that the substation had prepared itself for the transmission of a check code to indicate at the office the selection made at the substation in response to the selection code transmitted from the office. The check sending control relay 525 has been described already as being energized as a result of the energization of the point switching relay 4 I 5.

Upon the energization of relay a circuit is completed for relay H3 in multiple with the relay from positive battery over armature tilt-ail and its back contact, armature 4!-c and its front contact, armature 4Hc and its back contact, armature 525f and its front contact and through the winding of relay M3 to negative battery.

Energization of relay 526 also completes a circuit for sending code relay 522 in multiple with relay EH2 from positive battery through armature 4Mb and its front contact of relay AM, winding of relay 415, front contact and armature B i2-a, front contact and armature 529-0, front contact and armature 52Bb, armature 526-49 and its front contact and through the winding of relay 522 to negative battery. The particular sending code relay, such as 522, which is energized at this time is determined, it will be noted, by the particular point selection relay H2 which was energized in response to the point selection code received from the office so that the check code transmitted to the office will indicate the particular point selection which has been made at the substation.

As in the case of the corresponding relays at the ofiice, relay 522 at the substation will control at its armatures 522a and 522-b the particular polarity to be impressed upon the conductors L! and L-2 from the substation. At this time relays 264, M2, M3, M4, M5, 522, 526, 528, 529, SM! and SIZ have been energized at the substation. A circuit is now completed for the slow relay 435 in response to the energization of relay H3 described above. This circuit extends from positive battery over armature 4@2a and its back contact of relay 4G2, armature 5]la and its back contact break contact of armature 40'lb, armature Ml-11 and its back contact, front contact and armature 4l3--b, armature 40tb and its back contact and through the winding of relay 495 to negative battery.

Relay 405, upon energization, completes the impulsing circuit for the code to be impressed upon the conductors L! and L2. This circuit extends from positive battery over front contact and armature 522b of relay 522, back contact and armature 52ib, front contact and armature 4Ei5a to the conductor L2, while negative battery is applied through a resistor over front contact and armature 522-a, back contact and armature 52l--a to the conductor L-l.

A further result of the energization of relay M3 and the energization of relays 935 and 522 is to complete a circuit for the point checking relay 416 from positive battery over armature 464-1) and its front contact of relay 494 through the winding of relay M5, front contact and armature 6l2-a, front contact and armature 529--c, front contact and armature 528-4), front contact and armature 522-c, back contact and armature 52l-c, back contact and armature l l 9c, front contact and armature 465-0, armature Gilt-a and its front contact, armature til-b and its back contact, break contact of armature il6b, and through the winding of relay M5 to negative battery. Relay W3 closes a locking circuit for itself over armature H6b and its front contact, back contact and armature NS-c to positive battery over armature Mi l-b and its front contact. This point checking relay M6 controls the functions to be described in detail hereinafter.

As a result of the energization of relay 455 at the substation a circuit is completed for relay M36 from positive battery over armature t2a and its back contact, armature ich-a and its back contact, armature QUE-22 and its front contact, and through the winding of the slow relay 396 to negative battery. Slow relay iilfi, upon energizing, opens the circuit of relay Gilli to terminate the checking code impulse. Relay 485 is a slow-to-deenergize relay and will remain energized during the period While the operations in response to the receipt of the check code occur at the office.

At the office, in response to the particular polarity of the impulse transmitted over conductor L-i and L2, a circuit is completed through the relay Hi2 thereat. This is because of the fact that the rectifiers E62 and !83 are so arranged that only current flowing in the direction indicated will flow through the winding of relays It and I62.

This circuit is completed from conductor L-Z through armature Hi5-a and its back contact, armature l59-a and its back contact, armature Hie-a and its back contact, resistor l'BI, rectifiers I52 and through the winding of relay I62 to the conductor L-|.

Relay I02, upon energization, completes a circuit for the point checking relay I it at the oflice from positive battery over armature Hit-b and its front contact of relay I34, through the winding of relay H5, front contact and armature 3 I2-a, front contact and armature 229 0, front contact and armature 228-4), back contact and armature lfi3b, front contact and armature l02--c, back contact and armature lei-12, back contact and armature i65--c, armature H3a and its front contact, armature il7-b and its back contact, break contact of armature Hiib and through the winding of relay MS to negative battery. It should be noted that the point checking relay H6 finds a circuit for itself only if the negative line relay m2 at the office is energized in response to the checking code, which circuit was prepared by the energizaticn of the point selection relay 3 l 2 when the point selection was made at the office and its completion at this time by the energization of the negative line relay lll2 indicates a correct point selection at the substation. At this time the relays Hi2, ace, IH, H2, H3, H4, H5, H6, 228, 229, 268 and 3l2 are energized at the office.

Referring now to the substation, upon energization of the slow relay 466, the circuit for relay 495 was opened. Relay 4435 is a slow-to-deencrgize relay and remains energized while the above described operations occur at the office. Relay H35 now deenergizes, however, and a circuit is thereupon completed for the check switching relap 4!! from positive battery over armature 4B2a and its back contact, armature tel-a and its back contact, armature lth-b and its back contact, armature 4l6-a and its front contact, armature 4,1:8--a :and its'back contact, break contact of armature 411-4: through the winding of relay 411 to negative battery. Energization of relay 4.11 opens the circuit for relay 528 at its armature 411- and relay 528 is deenergized.

It should :be noted at this time, that while the substation selection was made by the transmiss-ion of a group selection followed by the transmission of a point selection, the checking operations of this selection are in the reverse order, i. e., the point selection is first checked and thereafter the group selection is checked.

Energization of relay 411, in addition to deenergizing the relay 528, energizes the group control relay 521 over a circuit from positive battery through armature 420-,a and its back contact, armature 414-c and its front contact, armature 4.111c and its front contact, and through the winding of relay 421 to negative battery. As a result of the deenergization of relay 523, the circuit of the sending code control relay 522 is opened and this relay is deenergized. At this time the relays 404, 406, 412, 413, 414, 415, 416, 411, 526, 521, 52-9, 540 and 612 are energized at the substation and a circuit is completed for relay 521 from positive battery over armature 494-?) and its front contact, through the winding of relay 414, front contact and armature 529a, front contact and armature 521-a, armature 526-.a and its front contact through the winding of relay 521 to negative battery. Relay 521, like relay 522, controls the transmission of a particular polarity over the conductors L1 and L2, but the polarity is reversed from that controlled by the relay 522, thus negative battery at the substation is applied over the armature 521- 1) and its front contact, front contact and armature 405-.a of relay 405, when this latter relay is energized as will now be described, to the conductor L-2. Positive battery is applied to the conductor L--1 over front contact and armature 521-a.

At this time the slow relay 406 has dropped out and a circuit is again completed for relay 405, as described hereinbefore. Energization of relay 405 completes the transmission of the group check code of predetermined polarity over conductors L---! and L-2. Energization of the relay 405 also completes a circuit for the group checking relay 418 from positive battery over armature 404-5 and its front contact through the winding of relay 414, front contact and armature 529-4., front contact and armature 521-c, front contact and armature 521-c, back contact and armature 4|9c, front contact and armature 405-c, armature 413-a and its front contact, armature 411-4) and its front contact, break contact of armature 418h and through the winding of relay 418 to negative battery.

Relay 418, upon energization, completes a locking circuit for itself from positive battery over armature 404-b and its front contact and through a resistor and front contact and armature 419-1). As a further result of the energization of relay 4135, relay 405 is energized over the circuit which has been traced before and this relay in turn opens the circuit of the relay 495.

' Relay 405, however, is a sloW-to-deenergize relay 41 1--b and its back contact, front contact and armature 413b, armature 406-1) and its front contact, front contact and armature 418c and through the winding of relay 401 to negative battery. Relay 401 looks itself over its own armature 401-b and front contact. Relay 401, upon energization after the transmission of the group check code, prevents the substation from transmitting any further codes to the oflice until the office has transmitted some code back to the substation.

.At the office, following the termination of the point check code upon the first deenergization of relay 405 at the substation, the negative line relay 102 is deenergized. At this time relays 104, 111, 112,113, 114, 115, 116, 228, 22-9, 240 and 312 are energized at the office. A circuit is now completed for the check switching relay 111 at the oflilce to switch from the point check to the group check. This circuit extends from positive battery over armature 102-a and its back contact, armature 191-41 and its back contact, armature 105b and its back contact, armature l1 6a and'its front contact, armature 118-0, and its back contact, break contact of armature H1a and through the Winding of the check switching relay 111 to negative battery. Check switching relay 111, upon energization locks itself from positive battery over armature 104b and its front contact, armature 1 19a and its back contact, front contact and armature H1-a, and through the winding of relay 111 to negative battery. Relay 111, upon energizing, conditions the office for the receipt of the group checking code. Upon energization of relay 111 the circuit for the point control relay 22B is opened. at the armature H1-c of relay H 1 and relay 228 deenergizes. A further result of the energization of relay 111 is to complete a circuit for the group control relay 221 from positive battery over armature 120-a and its back contact, armature H4b and its front contact,

armature 111-42 and its front contact and through the winding of relay 221 to negative battery.

After these operations are completed, the substation transmits the group check code in the manner described above and the polarity impressed upon the conductors L-1 and L 2 is such that current can flow only in the circuit including relay 101. Relay 101 is accordingly energized. At this time relays 101, I04, 111, H2, H3, H4, H5, H6, 111, 221, 229, 240 and 312 are energized at the office. The energization of relay 101 completes a circuit for the group checking relay 11 8 from positive battery over armature l04b and its front contact, winding of the relay 114, front contact and armature 229-11, front contact and armature 221-a, back contact and armature 103-4, back contact and armature 102b, front contact and armature 101-b, back contact and armature 105c, armature H3a and its front contact, armature H1--b and its front contact, break contact of armature 11 8--b and through the winding of relay 118 to negative battery.

It should be noted that this circuit depends for its completion upon the receipt of the proper group checking code which energizes the relay 101. The energization of the group selection, relay 229 prepared the above circuit for the relay I 18 and only upon the receipt of the proper code to complete this circuit at the armature of relay 191 is the relay 118 energized. As a result of the energization of the group checking relay 118 the check lamp 392'is illuminated over a circuit from positive battery, through the armature 1 18-4: and

its front contact, armature 312-0 and front contact of relay 312 and through the lamp 302 to negative battery. This lamp is individual to this particular selection and gives an indication that the checking codes received from the substation have been properly compared with the selection set up at the oflice, thus assuring the operator that the selection at the substation is correct.

At the substation the slow relay 405 is by this time deenergized as a result of the energization of relay 4015 and relays 404, 406, 401, 412, 413, 414, 415, 415, 411, 418, 521, 526, 521, 529,540 and 612 are at this time energized. Upon deenergization of relay 405 the final checking relays 419 and 420 are energized in series from positive battery over armature 402-a, and its back contact, armature 401-a and its back contact, armature 405-1) and its back contact, armature 416-a and its front contact, armature 418-a and its front contact and through the windings of relays 419 and 420 to negative battery. Energization of the relay 419 opens the checking circuit at armature 419-0 and also opens the locking circuit for relays 415 and 411 and these relays are deenergized. Relay 419 also closes a locking circuit for itself and for relay 420 over front contact and armature 419-a. Energization of relay 420 opens the circuits of relays 413, 526 and 521 all of which find their circuits over the back contact of armature 420-a of relay 420. Deenergization of relay 525 in turn opens the circuit for relay 521 at the substation.

A result of the deenergization of relay 413 is to complete a circuit for relay 524 from positive battery over armature 420-11 and its front contact, armature 413-0 and its back contact, armature 512-0 and its front contact, armature 632-b and its back contact, and through the winding of relay 524 to negative battery. It is to be noted that this circuit includes the back contact 632-1) of relay 632, which is controlled by the condition of its associated circuit breaker, being deenergized when the breaker is tripped. When the breaker is closed relay 532 is energized and the above traced circuit will energize relay 523 over front contact 632-17, instead of relay 524 over back contact 632-1). In the meantime the slow relay 406 has deenergized because of the previous deenergization of the relay 405. Relays 404, 401, 412, 414, 415, 418, 419,420,524, 529,540 and 612 are now energized at the substation.

At the office, following the completion of the group selection code which energized the relay 118, the positive line relay 101 deenergizes and closes a circuit for the final checking relays 119 and 120 from positive battery, armature 102-a and its back contact, armature 101-a and its back contact, armature 105-1) and its back contact, armature HES-a and its front contact, armature 1 IB-a and its front contact and through the windings of relays 119 and 120 to negative battery. Relay 119, upon energization, opens the locking circuit for relays 116 and 111 and these relays deenergize. As a result of the energization of relay 120, the relays 113 and 221, which find their energizing circuits over the back contact and armature 129-11 of relay 120, are deenergized. A circuit is now completed for the sending code control relay 221 from positive battery over the armature 120-a at its front contact, through armature 312-0. and its front contact, the back contact 304-1) of the control key 304, back contact and armature 210-a, armature 201-a and its back contact, through the winding of relay 221 to negative battery.

A further result of the energization of relay 1 19 is to complete a circuit for relay 105 from positive battery over armature 102-a and its back contact, armature 101-a and its back contact, armature 111-0 and its front contact, armature 119-1) and its front contact, back contact and armature 149-a, armature 106-1) and its back contact, and through the winding of relay 105 to negative battery.

Relay 105 energizes to transmit a holding pulse to the substation which serves to maintain the selection thereat. It will be recalled that the sending code control relay 221 was energized just preceding the energization of relay 105 and, as in the case of the selection code operations described before, prepares a circuit for impressing current of a predetermined polarity upon the conductors L1 and L2. This circuit is now completed upon the energization of relay 105 and current flows over the line of such polarity that it can flow only through relay 401 at the substation, Relay 401 is thereupon energized and at this time relays 401, 404, 401, 412, 414, 415, M1, 418, 419, 420, 524, 529, 540 and 612 are energized. Upon energization of the relay 401 the locking circuit for relay 401 is opened and this relay is de-energized to permit the transmission of a supervisory signal from the substation.

At the oflice, following the energization of relay 105, a circuit is completed for relay 106, as has already been described, which in turn opens the circuit for relay 105. After an interval of time relay 105 de-energizes and terminates the holding pulse. The system is then in condition for the receipt of a supervisory code indicating the condition of the selected breaker. Relay 106 deenergizes shortly thereafter.

Upon the ale-energization of relay 105 at the oifice the holding impulse transmitted over the conductors L1 and L-2 terminates and relay 4131 at the substation is de-energized, closing a circuit for relay 405 from positive battery over armature 402-21 and its back contact, armature 401-a and its back contact, armature 401-17 and its back contact, armature 419-12 and its front contact, front contact and armature 415-1), armature 406-1) and its back contact, and through the winding of relay 405 to negative battery. Relay 405 energizes and in turn completes a circuit for relay 406 as traced hereinbefore. Energization of relay 406 opens the circuit of the slow relay 405 which, however, does not de-energize immediately, and also completes a circuit for the relay 401 as traced before.

It will be recalled that, following the transmission of the check code impulses, the sending code control relay 524 was energized over a circuit controlled by the condition of the selected breaker at the substation. When the relay 405 at the substation now energizes, the code selected by energizing relay 524 is transmitted over the conductors L-1 and L2. In the present case this code comprises an impulse of rectified half-wave pulsations from the source of alternating current at the transformer 500 and the circuit extends from the secondary winding of transformer 505 through rectifier 505, front contact and armature 524-b, back contacts and armatures 523-1), 522-1) and 521-1), front contact and armature 405-a over conductor L2 to the ofiice, through armatures and back contacts 105-a, 159-a and 150-a, resistor 161, rectifiers 162, winding of relay 102, over conductor L-l back to the substation, through armatures and back contacts 521-a, 522-a and 523 -a, armature 524 av and its front contact, and through a resistor back to the secondary winding of the transformer 596.

The rectifier 505 permits only one polarity of the alternating current to pass, thus producing a flow of pulsating current in the circuit described. This pulsating current flowing in the described direction, is received at the oilice and can only flow in the circuit of relay I 02 which is accordingly energized. Being of a pulsating character, the impulse also passes through the condenser I65, which does not pass a continuous direct current impulse, and flows in the circuit of relay I03 over the full-wave rectifiers I66 and I51, in multiple with the circuit for relay IIJZ. Relays I92 and I03 are therefore energized at the ofiice. As a result, the trip supervisory relay 208 is energized over a circuit from positive battery over back contact and armature I I3a, armature I il5--c and its back contact, armature IDi--b and its back contact, armature IUZ-c and its front contact, armature I03-b and its front contact, armature I.20-c and its front contact and through the winding of the relay 208 to negative battery.

It will be noted that this circuit depends for its completion upon the energization of the final checking relay I28 and also upon the receipt of the proper supervisory code which will energize both the line relay IE2 and the line relay I93. The other supervisory code, indicating a closed breaker, would have energized the closed supervisory relay 239, The energization of relay 2E8 completes a short-circuit around the supervisory lamp relay 322 from positive battery over armature 298-47 and its front contact, back contact and armature ZQQe-b, armature 3I2-b and its front contact to one side of the winding of relay 322, the other side of which is'connected to positive battery. As a matter of fact, the supervisory lamp relay 322 had been de-energized in a previous operation due to the fact that the breaker is assumed to be tripped and a circuit had been completed for the green supervisory lamp 365, indicating a tripped condition of the breaker, from positive battery, armature 322.-c and its back contact, through the green lamp 335 to negative battery.

At the end of the supervisory code impulse,

- terminated by the de-energization of relay 465 at the substation, the relays I62 and M3 at the office are de-energized and in turn de-energize the trip supervisory relay 268. A circuit is now completed again at the ofiice for relay I05 as traced before. At the substation the relay 465 has in turn de energized the relay 4%.

Energization of relay I35 at the oflice causes the transmission of another holding impulse in the manner already described in detail above, which is followed by the transmission of a trip supervisory code signal from the substation. These operations are repeated indefinitely as long as no action on the part of the operator takes place, or as long as the selected breaker does not change its condition.

In order to close the breaker, the dispatcher turns the individual control key 304 from the trip position shown in the drawings to the close position and then operates the master control key 26! until he is advised by the changing of the super: visory lamps that the desired operation has taken place.

When the control key 304 is turned to the close position, the disagreement lamp 3% begins to flash and continues to do so until the control key 304 is, again brought into agreement with the position of the associated breaker as indicated by its supervisory lamp relay 322. Turning of the key 304 closes a circuit for the lamp Sill and relay 235 in series from positive battery over armature 322-; and its back contact, front contact 304-41 of key 304, lamp 3!] I, and winding of relay 235 to negative battery. The winding of relay 235 is of sufiiciently high resistance so that lamp 3III will not glow in series with it, but relay 235 will operate in series with the lamp 33! and close an obvious circuit for relay 236 which in turn shortcircuits the winding of relay 235. This causes the lamp 3M to glow with full brilliancy and deenergizes slow relay 235. After an interval of time slow relay 235 releases, in turn de-energizing slow relay 236, which also releases after a short time, causing the cycle of operations to be repeated with the result that the disagreement lamp 30I is caused to flash.

The circuits are so arranged that the operation of the master control key 20 I, during the time a holding impulse is being transmitted from the oifioe, does not immediately change the holding impulse to a control impulse, but awaits the re-\ ceipt of the next supervisory code from the substation, so as to prevent any possible mutilation,

of the holding impulse.

Assuming that at the instant the dispatcher depresses his master control key 29!, supervisory signals are being received from the substation, and relays Hi2 and I03 are energized, the dispatcher obtains control of the system by the energization of the relay 2!. The circuit for the relay 201 is completed from positive battery over armature and front contact Iii4b, contact 20!?!) of master control key ZEII, front contact and armature I03-.c, and through the Winding of relay 201 to negative battery. The sending code control relay 22I which was energized over back contact ZU'I-a is now de-energized and the circuits are changed from a holding code to the transmission of a closing code by the energization of the relay 223 over a circuit from positive battery, armature I20-a and its front contact, armature 3I2d and its front contact, through front contact 304-?) of key 304, armature 2Il'I--b and its front contact, armature Zia-b and its back contact and through the winding of relay 223 to negative battery.

Relays I92 and I I33 will now de-energize, following the de-energization of relay set at the substation, and a circuit is thereby completed for the relay I05 as described before. Relay Hi5 upon energization, completes the circuit for the transmission of a closing code, the code character of which is determined by the energization of the relay 223. This code comprises a pulsating current in a pre-determined direction impressed upon conductors LI and L--2, the circuit being an exact duplicate of that described above for the supervisory code, except that the polarity of the pulsating current is reversed. This pulsating current is in such a direction that it can flow only in the circuit of the relay 40! at the substation and, being of a pulsating character, also passes through the condenser 4 55 and over the fullwave rectifiers 466 and :61 through the winding of relay 433, in parallel with relay 462.

Relays 4M and 433 at the substation are accordingly energized and at this time relays lili, 4%, till, M2, M4, M5, M3, M53, 12s, 52 1, are, 54in w and BIZ are energized at the substation. Ener gization of relay 40I opens the locking circuit for the relay 401 and this relay is de-energized. A further result of the energization of relays 40I and 403 is to complete a circuit for the close control relay 509 at the substation over a circuit from positive battery, back contact and armature 4I3-a, armature 405-c and itsback contact, armature 40Ib and its front contact, armature 402b and its back contact, armature 403--a and its front contact, armature 420-1) and its front contact, and through the winding of relay 500 to negative battery. Relay 500, upon energization, completes a circuit for the closing relay 642 of the breaker, associated with point selection relay 6I2 from positive battery, armature 460-b and its back contact, armature 500-c and its front contact, armature SIZ-b and its front contact, through the closing relay 542 of the breaker to negative battery. The closing relay operates the breaker over conductors 052 to its closed position.

At the office, energization of the relay I which started the transmission of the closing code, also energized the relay I05 which in turn opens the energizing circuit for the relay I05. Relay I05 deenergizes after an interval of time, terminating the transmission of the closing code. Circuits are now in condition for the transmission of a closed supervisory code to indicate to the dispatcher that the circuit breaker has been closed in accordance with the close code transmitted from the oflice. The operation of the breaker to its closed position energizes the relay 632 which is'controlled over the contacts of the auxiliary switch 682. As a result of the energization of the relay 032 the relay 622 is de-energized, due to the momentary opening of its locking circuit, at the contacts 032-a, and the circuit for the relay 524 is also opened, while a new circuit is completed over the front contact $32--b of relay 632, instead of the back contact 632b as traced above, and relay 523 energizes preparatory to the transmission of a new supervisory signal indicating a closed condition of the breaker.

After an interval of time the closing code transmitted from the office is terminated by the release of relay I05 thereat, causing relays 40I and 483 at the substation to de-energize.

As a result of the de-energization of relays MI and 403 the circuit for relay 509 is opened and this relay de-energizes. A circuit is also completed for the relay 405, as traced before, completing a circuit for relay 406 which in turn operates relay 401 over the circuits already traced.

The energization of relay 523 at the substation prepares a supervisory code to be transmitted over a circuit which is completed upon the energization of relay 405 and which controls the transmission of a pulsating current of a polarity opposite to that controlled by relay 524. The pulsating current transmitted over this circuit is in such a direction that it can only flow in the circuit of the relay IIJI at the oflice. Being of a pulsating character, this current also flows through the condenser I65, over rectifiers I66 and I6! through the winding of the relay I03, in parallel with relay IOI. Accordingly, relays IOI and I03 at the ofiice are energized.

Energization of relays IOI and I03 completes a circuit for the closed supervisory relay 209 from positive battery over back contact and armature II3a, armature I05-c and its back contact, armature IOIb= and its front contact, armature I02b and its back contact, armature I03-a and its front contact, armature I20-b and its front contact and through the winding of relay 209 to negative battery.

Relay 209, upon energization, completes a circuit for relay 322 from positive battery through the winding of relay 322, front contact and armature EIZ-b, armature 209b and its front contact and through a resistor to negative battery.

- Relay 322, upon energization, completes a locking circuit for itself over armature 322--b and its front contact, and at its armature 322-c opens the circuit for the green lamp305 and closes a circuit for the red lamp 303 indicating at the oflice that the circuit breaker has been closed. Relay 322 also opens the circuit of the disagreement lamp 30I which accordingly is extinguished.

Energization of the relay 209 also completes a circuit over contact ZOE-a for relay 2 In which is in multiple with the circuit for relay 223. Relay 2I0 upon energization opens the circuit for the relay 223 to stop the transmission of a further closing code and thereby to prevent pumping of the breaker.

In supervisory control systems the remote circuit breaker may be closed upon a short circuit and will then attempt to trip immediately. The dispatcher, however, may be unaware of this condition and unless provision is made for automatically opening the closing circuit upon receipt of supervisory signal indicating the closing of the breaker, the breaker may be held in a closed position against a short circuit.

In the present system this is prevented by the energization of relay 2I0 which, as described above, opens the energizing circuit of relay 223. At the same time a circuit is completed for the relay 22E over the front contact of the armature 2I0-b, thus substituting the holding code for the closing code even before the dispatcher releases the master control key 20 I.

At the substation, upon energization of relay 405 for the transmission of the closed supervisory code, relay 400 was energized which in turn energized relay 401 and a circuit was thereby completed for the point start relay 022. This circuit extends from positive battery over armature 40'I-c and its front contact, armature 6 I 2-b and its front contact, front contact and armature 632-a, and through the winding of relay 622 to negative battery. Relay 622 closes an obvious locking circuit for itself.

The operations described above for the transmission of a holding pulse from the office as a result of the energizing of relay RI and the transmission of a closed supervisory code as a result of the closed condition of the breaker are now continued indefinitely until another operation occurs at the ofiice or a change in the breaker condition occurs at the substation.

Following the receipt of the supervisory signal from the substation, indicating that the breaker has been closed, the dispatcher will release his master control key 25L Relay 201' at the office, however, will remain energized over a locking circuit extending over the armature I03-c and its back contact, and front contact and armature 20'I-c to positive battery over front contact and armature I94-b. This locking circuit for relay 201 is maintained until the next supervisory code is received to prevent mutilation of impulses in the event that the master control key is released while a code is being transmitted from the ofiice. When the next supervisory code is received relay M3 at the ofiice is energized, opening the locking circuit for relay 201. Relay 2I0 remains locked until the control key 304 is turned to the trip position or until the selection is released.

When the dispatcher releases the selection by the restoration of the point key 306, relay III releases to prevent the sending of further holding pulses after the next supervisory pulse from the substation is received. The transmission of pulses therefore stops and relays I04 and 404 at both ends release, in turn releasing all other energized relays and re-operating relays 22'! and 521 at both ends. At the substation relay 4H2 releases after a predetermined delay maintaining the circuit of the substation start relay 4II open for a short interval. This gives the dispatcher at the ofiice preference over supervisory signals and enables him to break in for any control operations he may desire, even though the substation may not have transmitted all of the supervisory signals for changes which have occurred.

In the foregoing a closing operation of the breaker has been described in detail. For tripping operation selections are made in exactly the same manner, except that a trip code is transmitted instead of a closing code. This is accomplished by the energization of relay 224 instead of relay 223 over back contact 304-1) of control key 304. Relays 402 and 403 at the substation are operated in response to this code to energize relay 508 instead of the operation of relays 40I and 403 to energize relay 509 asin the case of the close code. Similarly, relays I02 and I03 at the office are operated to operate in turn relay 208 instead of relays IOI and I03 operating relay 209. Relay 210 at the office in that case willnot operate. Relay 208 causes the release of the supervisory lamp relay 322 by short-circuiting its winding as described before. The release of relay 322 extinguishes the red supervisory lamp 303 and lights the green supervisory lamp 305 to indicate that the breaker is tripped.

The selecting and checking operations for other points are the same as those described hereinbefore for one particular point, except that other codes are substituted for the group and point selecting and checking impulses. In the operations described above, code #1 is used for group selection and group check, and code #2 for point selection and point check. The second point s'hownon the drawings is selected by sending code #1 for group selection and code #3 for point selection. The third point uses code #1 for group and code #4 for point selection, and

so forth. It will be evident that any one of the five possible codes may be used for group selection as well as for unit or point selection, so that 25 different combinations are possible with two selecting impulses. If a third selecting impulse were used, the number of possible combinations would increase to 125, and so forth.

In the foregoing a complete description has been given of all the operations which occur when a dispatcher at a control oflice selects, operates and supervises a remote circuit breaker located at a substation. The operations which occur, when a breaker automatically operates, to give an indication to the dispatcher of such operation, will now be described in detail except that where the circuits are the same they will not be given again in detail.

It will be assumed for purposes of illustration that the breaker associated with selection relay 0I2 has tripped from its closed position. At'this time the normal circuit conditions as described under control operations are the same; namelyrelay 221 in the office and relay 521, as well as the point start relays 622, 624, etc., in the substation are energized. The relay 632 is also energized at this time because of the circuit breaker being closed. Upon the tripping of the circuit breaker the circuit for relay 032 is opened at the contacts of the auxiliary switch 682 of the breaker and relay 632 de-energizes, in turn opening the locking circuit for relay 522 during the interval while the armature 032a of relay 632 moves from its front to its back contact. Relay 622, upon de-energization, opens its own locking circuit at front contact and armature 622c which prevents this relay from energizing again when relay 632 closes its back contact 632a. A circuit is thereupon completed for the start relay 4 and the sending code control relay 52I in series from positive battery through armature 404-b and its back contact of relay 404, armature 4 I2-b and back contact, through the winding of relay 4| I, through armature 40Ia and its back contact, break contact of armature 4I5-a, break contact of armature 4I4-a, armature Ii22-a and its back contact, and through the winding of relay 52I to negative battery. Relay 4H closes a new circuit for itself over front contact and armature 4| I-a, so that the subsequent operation of relays 404 and 4I2 will not open its circuit. 7

The circuit for pole-changer 540 is also closed over the armature 622-0 and its back contact to generate the necessary alternating current for the transmission of code signals. A circuit is now completed for relay 405 from positive battery through armature 402-a and its back contact of relay 402, armature 40I-a and its back contact, break contact of armature 40'I-b, armature 4! I-b and its front contact, back contact and armature 4l5-b, armature 405-12 and its back contact, and through the winding of relay 405 to negative battery. The energization of relay 405 completes the circuit for transmitting the code signal determined by the previous energization of relay 52 I As has already been described, energization of relay 52I applies negative battery to the conductor L-'2 and positive battery to the conductor L-I so that an impulse of a predetermined character is now transmitted over-the conductors L-i and L-2 to the ofiice. This impulse is, of course, in accordance with the group in which the breaker is located. A further result of the energization of relays 52I and 405 is to close a circuit for the relay 520 from positive battery over back contact and armature 4I3a, armature 405- c and its front contact, armature 4 I 9-c and its back contact, armature 52I-c and its front contact, armature 52l-a and its front contact,

and through the winding of relay 529 to negative battery. Relay 529 is the group selection relay for group #1. As will be described hereinafter, when a check code is received back from the office, indicating the selection made thereat, it must agree with the group selection made at the substation as indicated by the energized group selection relay 520 before the actual supervisory code for indicating the condition of the breaker can betransmitted to the office. A further result of the energization of relay 405 is to complete a circuit for relay 405 which, in turn, opens the circuit of relay 405, but relay 405 is a slow-to-deenergize relay and will not drop out until the operations to be performed at the ofiice are completcd. Energization of relay 405 also completes a circuit for the holding relay 404 which with its armature 404-1) functions to hold the selections made during the subsequent operations. Start delay relay 4I2 operates in multiple with relay 404 as described above.

At the oflice, in response to the particular'polarity of the impulse transmitted over the conductors L--I and L2, relay IN is energized. This is due to the arrangement of the rectifiers I63 which permit current to flow only in a predetermined direction in the circuit of relay IOI, this direction being in conformity with the polarity of the impulse transmitted over L-I and L-2 in the present case. In response to the energization of relay IOI at the oflice, a circuit is completed for the group selection relay 229 at the ofiice, from positive battery through back contact and armature 4I3a, armature I05-c and its back contact, armature I0 I-b and its front contact, armature I02-47 and its back contact, armature I03--a and its back contact, armature 221-11 and its front contact, and through the winding of relay 229 to negative battery.

It will be noted that the circuit now established is different from the circuit traced when operations originated at the oflice, insofar as the circuit for relay 229 is completed over the armature of relay IOI in response to a code received from the substation, instead of being closed over the armature of relay 22I which is the corresponding sending code control relay energized in response to a code originated at the oflice.

As a further result of the energization of relay IN, a circuit is completed for relay I04 from positive battery over the armature I02-a and its back contact, armature IOI-a and its front contact, and through the winding of relay I04 to negative battery. Relay I04, as in the previous case, functions to hold the selection relays operated during the remaining selecting operations thereby performed, and also to open the circuit of start relay III, so that no operations can be originated from the office, until the supervisory operation originated at the substation is completed. A circuit is also completed for the polechanger 240 over front contact and armature I04a of relay I04, to keep the pole-changer 240 in operation until the supervisory operation is completed.

At this time, therefore, relays l0I, I04, 221, 229 and 322 are energized in the ofiice, the latter relay being energized to indicate the closed condition of the breaker prior to the receipt of the trip supervisory signal now being transmitted.

At the substation, in response to the energization of the relay 406, the circuit for relay 405 was opened and this slow relay now de-energizes. A circuit is thereupon completed for relay M4 in series with relay 529. Heretofore this series circuit was not effective because of the fact that the energized relay 405 provided a by-pass around the winding of relay 4I4. Relay M4 is provided with a make-before-break contact 4I4-a and upon the energization of this relay the circuit for relay 52I is opened while a new circuit is completed for the relays 4H and 522 in series from positive battery over armature 404-b and its front contact, armature 4I Ia and its front contact, through the winding of relay 4| I, armature 40I-a and its back contact, break contact of armature 4I5-a, armature and front contact 4I4--a, armature 529-g and its front contact, armature 622-b and its back contact, and. through the winding of relay 522 to negative battery. As a further result of the energization of relay M4 the circuit for the group relay 521 is opened and this relay de-energizes. A circuit is in turn completed for the relay 528 as traced hereinbefore. Relay 528 prepares the substation for the selection of one of the points in the selected group. At this time relays 406, M I, M4, 522, 528, 529 and 540 are energized at the substation.

At the ofiice, following de-energization of relay 405 at the substation and the termination of the group selection impulse, relay IOI de-energizes and a circuit is completed for relay H4 in series with relay 229. As in the case of the substation, relay I I4 was heretofore by-passed by the energized relay IOI and upon de-energization of relay IOI this by-pass is removed, permitting energization of relay I I4. Relay 221 is de-energized upon the energization of relay H4 and in place thereof a circuit is completed for relay 228 over the front contact and armature 4I4b. Relay 228 is the point control relay at the oflice.

At the substation, following the de-energization of relay 405 as a result of the de-energization of relay 405, the circuit for relay 405 is again completed and this relay energizes. Relays 405, 4H, M2, M4, 522, 528, 529 and 540 are then energized at the substation. Energization of relay 405 completes a circuit for relay 6I2 which is the point selection relay associated with the tripped breaker. This circuit extends from positive battery, back contact and armature 4I3a, armature 405c and its front contact, armature 4I9c and its back contact, armature 52I-c and its back contact, armature 522-0 and its front contact, armature 52Bb and its front contact, armature 529-0 and its front contact, and through the winding of relay 6I2 to negative battery. A further result of the energization of relay 405 is to complete a circuit for relay 406 which in turn opens the energizing circuit of the slow relay 405.

A further result of the energization of relay 405 is to complete the transmission of a code impulse for the point selection in accordance with the energized relay 522 which impresses positive battery on the conductor L--2 and negative battery on the conductor L-I.

At the office, in response to this impulse, current can flow only in the circuit of the relay I02 which accordingly is energized and. in turn completes a circuit for the point selection relay 3I2 at the office, from positive battery over the back contact and armature II3-a, armature I05c and its back contact, armature IOIb and its back contact, armature I02-c and its front contact, armature I03b and its back contact, armature 228b and its front contact, armature 229c and its front contact, and through the winding of relay 3I2 to negative battery. The relay 3I2 energizes to indicate the point selection received from the substation.

At the substation, relay 405 is de-energized after an interval of time following the completion of the above described operations at the office. A circuit is thereby completed for relay M5 in series with the relay 6I2, as described hereinbefore. Energization of relay 4|5 opens the circuit for relay 522 which drops out at this time, while the circuit for 'relay 4 is maintained over armature 4I5a and its front contact to negative battery through a resistor. As a further result of the energization of relay 4I5, a circuit is completed for relay 4I3 from positive battery over armature 420--a, and its back contact, armature 4 I 5a and its front contact, armature 4I I-c and its front contact, and through the winding 

